A fuel cell vehicle is driven by using electricity generated from a fuel cell stack serving as a main energy source. Such a fuel cell vehicle is additionally equipped with a high-voltage battery, such as a battery used for a hybrid electric vehicle (HEV), that serves as an auxiliary energy source for driving the fuel cell at the initial stage of start-up.
Conventionally, in the start-up process of a fuel cell vehicle, both an electric vehicle (EV) start-up operation (such as an operation used for driving a vehicle with only a high-voltage battery) and a fuel cell (FC) start-up (such has an operation used for driving a fuel cell) are performed at the same time. In this case, a battery having the same specification as a low-voltage battery (e.g., a 12 V battery of an internal combustion engine vehicle) is used for the driving power of the operating controllers used during the start-up operation and of the power supply for various kinds of valves (hydrogen supply valve, etc.). When the performance of such a low-voltage battery is lowered to a certain level or less, the low-voltage battery is rapidly degraded to a level at which the fuel cell vehicle cannot be started, as in the case of an internal combustion engine vehicle.